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ANA 534 External Ear

learning objectives answers to external ear

Name the three ossicles of the middle ear cavity in order from lateral to medial.

Malleus, incus and stapes.

Name two muscles found in the middle ear cavity, their innervation and what they attach to.

Stapedius, CN VII, the stapes; tensor tympani, V3, the malleus.

Name the region of the tympanic cavity found above the head of the malleus.

The epitympanic recess.

Identify an anterior communication of the middle ear cavity and to what does it communicate?

The auditory tube, the nasopharynx.

Identify a posterior communication of the middle ear cavity and to what does it communicate?

The aditus of the mastoid antrum, mastoid air cells.

Name two nerves associated with the middle ear cavity

CN VII and CN IX

What branches does the facial nerve give off to the middle ear cavity and what modalities do they carry?

The nerve to the stapedius (motor) and the chorda tympani (taste to anterior 2/3 of tongue).

What branches does the glossopharyngeal nerve give off to the middle ear cavity and what fibers are carried in it?

The tympanic branch that contributes preganglionic parasympathethetic fibers to the tympanic plexus.

What two major vessels have an inferior relationship to the middle ear cavity?

The internal jugular vein and internal carotid artery.

What fibers travel on the surface of the internal carotid artery and to what to they contribute?

Postganglionic sympathetic fibers (the carotid sympathetic plexus) that are contributed to the tympanic plexus.

Identify the bulge on the medial wall of the tympanic cavity and what causes it?

The promontory, the cochlea of the inner ear.

Define the umbo and pars flaccida.

The umbo is the point of attachment of the manubrium of the malleus to the tympanic membrane. The pars flaccida is the uppermost portion of the tympanic membrane that lacks a central fibrous layer and is therefore not as rigid.

Name one branch given off the intraosseous portion of CN VII that is NOT related to middle ear structures. What kind of fibers travel in this nerve?

The great petrosal nerve. Preganglionic parasympathetic fibers.

Name two openings in the medial wall of the tympanic cavity and which of these contains the footplate of the stapes?

The oval window and round window. The oval window is filled by the footplate of the stapes

What is the bony cave in the petrous temporal bone forming the middle ear called?

The bony labyrinth.

What lines this cavity?

The membranous labyrinth.

What fluid is found within the membranous labyrinth? Between the bony and membranous labyrinth?

Endolymph. Perilymph.

What structure(s) of the middle ear comprise the portion dealing with hearing?

The cochlea and cochlear ducts.

What structure(s) of the middle ear comprise the portion dealing with balance?

The 3 semicircular canals.

The cochlear duct divides the cochlea into which two spaces?

A superior scala vestibuli, an inferior scala tympani.

What is responsible for detection of sound vibrations?

The organ of Corti in the flat inferior aspect of the coclear duct - the basilar membrane.

Which division of CN VIII deals with hearing? With detection of balance/ acceleration?

The cochlear division. The vestibular division.

What specialized areas of the semicircular canals are responsible for detection of balance/acceleration?